DNA nanosphere-enhanced DNAzyme system for sensitive and rapid detection of lead contamination in water and living cells

Lead (Pb^2 +) contamination poses significant risks to human health and the environment, necessitating the development of sensitive and rapid detection methods. In this study, we present a DNA nanosphere-enhanced substrate strand-DNAzyme (DS-Sub-Dz) system for the efficient detection of Pb²⁺ in both environmental and biological samples. The DS was constructed by annealing single-stranded DNA with four palindromic regions and extending sequences at the terminals, simplifying the process and reducing costs compared to traditional long DNA strands. The Sub-Dz, modified with fluorophore (FAM) and quencher (BHQ1), was then grafted onto the DS surface, forming the DS-Sub-Dz system through a hybridization reaction. This system utilizes spatial confinement and a cleavage recycling reaction to amplify the fluorescence signals of FAM, enabling highly sensitive and rapid detection of Pb²⁺ over a range of 2 nM to 40 μM. With a detection limit (LOD) of 2.0 nM-1000 times lower than the control Sub-Dz system-the DS-Sub-Dz demonstrated exceptional sensitivity. Further tests confirmed its ability to distinguish between various heavy metal ions in tap water. The enhanced cell internalization efficiency, accelerated reaction kinetics, and improved biostability of the DS-Sub-Dz system also enabled successful Pb²⁺ detection in both water samples and intracellular imaging, showcasing its potential for monitoring lead contamination in environmental and body safety applications.